While I here working in St. Thomas I've been able to do a fair amount
of diving. The most fun one so far has been diving in the ship
channel.
We picked a day with no cruise ships moving around. Duh!

But because of the cruise ship traffic in and out of the harbour the
bottom of the channel is turned up on a regular basis. In fact the
bottom, due to the prop wash of the ships, looks a lot like what you
would see after a treasure salvage ship with mailboxes got done
blowing out the bottom. And you can find all kinds of cool bottles and
stuff dating back 100 - 150+ years ago as well as new cruise ship
junk.
There is a local here who owns a real old time do it all dive shop
that has hundereds of bottles in his shop and at his house. He told us
it's not uncommon to find cannon and musket balls as well as coins.

Of course since you are diving in the ship channel no dive shops
offers this as a dive. Not to mention it's probobly not legal from a
USCG stand point as well. :-)

But it's real cool. And you find lots of broken pieces of bottles and
china as well as whole ones.
The depth is only around 35 feet so you have tons of time and the
ships come and go several times a week so there is freshly turned
bottom to search all the time.

On this one dive 2 out of  the 3 of us doing the dive got a whole
bottle. I was the odd man out so I'm going to try and hit it a couple
more times before we leave to get one for myself.

Anyway, if you're ever in St. Thomas, have access to a private boat
and understand the risks, it's well worth a shot IMHO.